Method of manufacture of piston-rings



W. A. OUBRIDGE. METHOD OF MANUFACTURE OF PISTON RINGS.

APPLICATION FILED OCT. 6, 1919.

Patented July 19, 1921.

UNITED STATES.

PATENT OFFICE.

WILLIAMA. OUBBIDGE, OF COVENTRY, ENGLAND.

Application filed October 6, 1919. Serial No.

To all whom it may concern;

Be it known that I, WILLIAM ARTHUR Ounmnen, a subject of the King of Great Britain and Ireland, and residing at Haldon, Park Road, Coventry, in the county of Warwick, England, have invented an Imgroved Method of Manufacture of Pistonings, and of which the following is a specification.

The object of my invention is, with certainty and economy of manufacture, to produce piston rings, which shall give and maintain during operation a more perfect uniform pressure on the cylinder wallsthan has been obtained hitherto.

It can be theoretically demonstrated that a self expanding. piston ring, in order to produce uniform spring packing pressure upon the cylinder wall, should conform to and maintain in its free state a peculiar curve (hereinafter referred to as the selected curve) which may be obtained by taking a split ring of truly elastic material 6. 9., steel devoid of all latent stresses and of circular form, and fixing such ring in its outsprung state by the insertion of a distance piece. Y

Inthe accompanying drawings Figure 1 is va diagram of the selected curve" above mentioned. i

Fig. 2 is a sectional view of a machine for use in the manufacture of piston rings according to this invention and Fig. 3 is a plan view of a detail of the machine shown in Fig. 2. a

. The curve, which is illustrated by Fig. 1, is the involute of a. cycloid generated by a rolling circle whose diameter is proportional to'the pressure which the ring is intended to exert. As shown in Fig. 1 the complete'evolute for the whole ring is two smallwaves of the cycloid. A pencil at the end of a string of length K. A. fastened to K would describethe curve, if, as the penoil moves the string winds on the curve K. L; or J. i

If a piston ring is to be manufactured to give and maintain uniform pressure on the cylinder wall, it is by no means sufficient to merely take a ring blank and out a gap out of it. Some treatment must be applied to the ring blank which will make it, when split and in the free-state conform to and maintain the above mentioned peculiar i 65 curve.

Specification of Letters Patent.

'mg on a copying lathe Patented July 19, 1921. 328,715.

Before my invention various methods have been suggested and applied to the manufacture of piston rings, with the obect of making the rings approximately round, so that they should exert approximately even pressure on the cylinder wall.

no such method is to hammer the split ring cold externallyadjacent to the tips so as to make the radius of that portion of the ring approximate to the cylinder radius. Another method proposed with the like ohect, 1s to heat the split ring locally adj acent to the tlps, and to bend it in that condition so that the end portions are caused to con form to a segment of a circle, whose diameter 1s' less than the untreated portion of the ring. By neither of the foregoing methods of manufacture can the ring be made to conform to and maintain the selected curve in its free state, or when extended and 1n operation in the cylinder, maintain its desired circular form nor was it the object of either of such methods of manufacture to utilize the property of the selected curve. A third method of manufacture, suggested and applied before the date of my appllcatlon, is to make an undivided ring blank conform to a desired shape by form turning, that is to say, by cutting up a castfrom a dummy, the form of whlch is derived by calculation, or by springing outward a splitring of circu. lar form, and fixingthe same in its outsprung state. a,

In all the foregoing previousmethods of manufacture stresses are generated and left in the ring, which arise fromthe heat conditions involved in cooling of the casting,.-the

hammering, local heating, or turning as the case may be. Such stresses are deleterious, in that, though thering may be fairly of the shape intended when made, it will often while at a red heat, the ring blank is subjected to pressure between dies so formed as to cause the ring to conform as near as may be to the selected -curve-(III) the pressed ring is uic'kly-removed from the inner die, and (I thering is subjected to a judicious re-heating' and" regulated cooling operation where necessaryor desirable.

In addition to the foregoing steps, it will be understoodithat the common operation of gapping the blank ring, or removing a part therefrom,*may also be performed as a step in theman'ufacture of the finished piston ring. r V The respective objects and purposes of each of the successive steps in my method of manufacture are these I By heating to a red heat before shaping, every trace of stress is taken out of the blank. By shaping the ring at a red heat, it is made: to conform to the selected curve 'w.itho'ut generating any stress in the ring, and uniform pressure of the ring on the cylinder wallis secured tothe highest possiblevdegree by the utilization of the properties of the selected curve. "Thequick removal from' the inside die minimizes the tendency to generation of stresses'fbywtoo quick coolingand prevents the ring from splitting or breaking, if it be desired to bring it off the said die in the unsplit condition. The judicious re-heating and regulated cooling operation also prevents the generation of stressesin the finished ring. The operation of judicious reheatingand regulated cooling may be carried out without in any way altering the shape of the ring. a If properly carried out my method or process of'manufacture results in the production of a-ring which is of the correct shape, free from all latent deleterious stresses and thereby insures the production and maintenance of uniform pressure on the cylinder walls during working conditions to a greater extent than'has hitherto been accomplished. 7

I-Iaving now particularly described and ascertained the'nature of my invention, I will now proceed to describe how, by means of a suitably constructed machine, it may so far asI know, be best performed.

Fig. 2 of the accompanying drawings illustrates, in sectional side elevation, a machine'suitable for the purpose.

'" On a standard or bed is carriedthe table 0 having mounted thereon a furnace b which may be of any suitable kind, for example,

, electric or gas heated, and in this furnace the rings A '(which in this instance are shown as uncut),to be shaped, are placed ina pile, one above another, for being heated to a red heat andready for shaping. At its lower end the furnace has an openingc sufficiently large to allow the passage therefrom of' a single ring at a time, pushed essential through it by a slide d adapted to run to and fro beneath the furnace Z) and relatively to the table a.

This slide d is operated through a lever a pivoted to the slide at f and at its opposite end pivoted to a stationary part 9 where it is slotted to allow its upper end to travel in a horizontal line. This lover a is connected by a link i to the lower end of a cam-lever j which is pivoted to the frame of the machine at and which carries a cam-roller Z arranged to engage the periphery m of a power driven cam m ada )ted to relatively slowly withdraw the slide d after it has ejected a ring from the furnace and, when at the end of the withdrawal stroke, to suddenly return and eject the next succeeding ring which, in turn, pushes the ring just previously ejected, from the position to which it has been restored after being shaped by means to be hereinafter described, thus causing the said previously ejected ring to pass to the chute n, down which it slides into a suitable receptacle 0.

Adjacent the furnace b there is carried on the table a, a mandrel 1) having its upper end made conical so that rings placed over it may be automatically guided into position upon it when a platen q, carried by rods 1', 1, is drawn down to force the red hot ring A on the mandrel p. The inner die or mandrel 19 and its corresponding outer die or platen g are so shaped that they will by pressure, give to the red hot ring the contour of the selected curve. The rods 1, 1 are yieldingly mounted about two-thirds of their length from the said platen, in a frame 8 and below the said frame 8 they are furnished with nuts 1', 1 and with springs r 9" encircling them and interposed between the said nuts and the frame 8, so as to cause the frame 8 to be normally retained against shoulders 1 1' on the rods 0', r by the springs 1, 0 Below the nuts 9, r the downwardly extending portions of the rods 9", 'r are adapted to slide through a stationary plate 6 and they have collars r 0 on their lowermost ends below the plate t, pinned to them so as to limit their upwardmovement relatively to the stationary plate t, while between the latter and the nuts 1, 1- are interposed springs u, a which tend to keep the rods 9, '1', frame 8 and the platen q in their highest positions. The frame 8 carries a cam-roller 8 adapted to engage the periphery of a cam 11 carried on the same shaft as the cam m and adapted, once in every rotation, to press its part of longest radius into contact with the cammandrel p, proceeds at once to cool and therefore to contract, and if it be nicked before being heated the contraction on the mandrel may be made to cause the ring to fracture at the nick when the temperature is sufiiciently reduced, in this way dispensing with a separate operation for the purpose of splitting the ring.

In practising this invention it is required to prevent the cooling of the ring while on the mandrel, after shaping. To this end the shaped ring is pushed quickly from the mandrel by means of a third cam w, mounted on the same shaft as the cams m and o. Surrounding the mandrel is a ring-like plate a: mounted on three rods ca 00*, m as shown in Fig. 3, adapted to pass through the table a and carried at their lower ends by a frame y furnished with a cam-wiper a. The rotation of the cam w is so timed that immediately after the ring has been forced upon the mandrel 39 its part w of greatest radial length raises the wiper 2 together with the frame 3 rods .22 and annuloid plate as and so forces the ring from the mandrel to the free position from which it is pushed to the chute n by the next succeeding ring ejected from the furnace b.

To restore a normal unhardened condition to the shaped rings, they are next heat treated, when and as the composition, weight or size of the ring require, by judicious reheating and regulated cooling and for this purpose, instead of being conducted by the chute n to a collecting receptacle they may be conducted to a conveyor adapted to carry them through a series of chambers in which they are successively subjected to temperatures ranging between about 600 centigrade and 1000 centigrade for a time that varies with each variation of the ring and is adapted to radually bring them to the required nondeIeteriously stressed state.

I claim 1. The method or process of piston ring manufacture,

which comprises the following essential steps, viz :-(I) raising the ring blank to a red heat; (II) conforming the ring blank, at a red heat to the selected curve, as near as may be, by pressure between suitably shaped dies; (III) uickly removing from the inner die, and (I8) regulating cooling, all substantially as hereinbefore described and for the purposes hereinbefore specified.

2. The method or process manufacture, which comprises the following essential steps, viz :-(I) raising the undivided ring blank to a red heat; (II) conforming by pressure from a platen the undivided ring blank at a red heat to the pcriphery of an inner die which periphery has been s aped to the selected curve; (III) quickly removing the conformed blank from the periphery of the inner die by pressure from a lower die; (IV) regulating cooling, all substantially as hereinbefore described and for the purposes hereinbefore specified.

WILLIAM A. OUBRIDGE.

Witnesses:

EVELYN WILLIAMS, EDWARD B. TULLY.

of piston ring 

